It's Quater Mess..

Ok - to set the record straight-ish, the rather excellent website Ringstone Round, has a great chronology of all published Quatermaterial so far:

http://kristian.sdf-eu.org/quatermass/chronology/

So that saves me a job of explaining that one! But just to outline a few basic plot points. There are four basic stories in the genre, which have appeared as Tv and film productions, but also under different names.

1. The Quatermass Xperiment - the first appearance, spread over film/tv. Broadcast in 1953 as a live TV production on BBC with Reginald Tate as the Prof. Only the first two episodes are available. Then it appeared as the 1955 Hammer film, with Brian Donlevy as an arrogant, hardnosed Prof, aimed at a more American audience. The basic premise is the British Rocket Group sends a rocket into space, which veers off course and during its wandering, is invaded by an alien conciousness, which promptly consumes two of the human crew and inahabits the third, Victor Caroon. Crash landing on Earth, Caroon is rescued and hospitalised. Unable to communicate and barely cognizant, Caroon struggles against the demands of the alien being inside him as it attempts to assimilate more living tissue. Caroon absorbs a cactus plant and an orderly and escapes from hospital, transforming en route. As the alien takes over Caroon, it finds its way into a London Zoo and feasts on the animals, becoming larger and more deadly in the process. As the creature has now gone beyond the bonds of humanity, it leaves a trail of slime and dead cells behind it, giving the Prof and the bumbling Police a means to track it down. Quatermass and his colleague realise that the creature - with it vegetable content has the ability to spawn other of its kind and that the time for sporing is imminent. Cue the showdown in Westminster Abbey as the alien seeks a place of safety to divide and spread its cells across London. Swift work by Donlevy and his cronies send hundreds of thousands of volts of electricity from the National Grid into steel scaffolding beneath the creature, which withers and fries in the nick of time. Donlevy subsequently stomps off under a cloud announcing he wants to "start again"

2. Quatermass II - Another BBC TV series with yet another actor as Quatermass, John Robinson. This ran just before the Hammer film release above, in 1955. A mysterious shower of meteors near a small village attract the Profs attention. On inspection, it is seen that the bolides - or rocket shaped meteors - are filled with some noisome gas, which leaves a wound on contact. Further investigation leads Quatermass to discover a vast secret installation in the english countryside, which bears an uncanny resemblance to his projected moonbase, with huge pressure domes. Infiltrating the base, it transpires that a shadowy company has built what appears to be a food treatment plant, but is in reality a vast containment plant for gestalt aliens, who are arriving by meteor from beyond the orbit of Jupiter. Individually, they are tiny unicellular entities, but once introduced to a suitable atmosphere in the domes, they coalesce into vast amorphous blobs of matter. Quatermass manages to sabotage their attempts at world domination and the creatures burst forth from their tanks, huge towering masses of gelid flesh and rampage across the base. Meanwhile a BRG rocket has been aimed at their orbiting control centre and as the rocket collides with its target, the aliens fall helpless, succumbing once more to the oxygen rich Earth atmosphere. Also released by Hammer in 1957 starring Donlevy.

3. Quatermass and the Pit - The pinnacle of the Quaterseries. 1958 BBC series, starring Andre Morrell as a dashing and charismatic Professor - probably my favourite incarnation, warm, caring, intellectual, but still determined and forceful. Filmed live at broadcast, the TV series is ambitious and beautifully acted. Also released in 1967 by Hammer in a colour production, with Andrew Keir and the lovely Barbara Shelley.
Extensions to the London Underground line at Hobbs Lane station reveal what appear to be human remains. Inspection shows they are in fact prehistoric remnants and attempts are made to secure the discoveries before work can re-commence. During the dig, what appears to be an unexploded bomb is revealed and the Army descend on the station, much to the annoyance of Matthew Roney, who is in charge of the recovery. In trying to bring press attention to the fossils, Roney bumps into Quatermass who is drowning his sorrows at the governments secondment of the British Rocket Group by the military. Roney convinces the Prof to look in at Hobbs Lane and Quatermass enlists the unwilling help of Colonel Breen, who he has been forced to work with. Breen briskly orders everyone out and has the earth around the UXB removed, to reveal an alien spaceship. With Quatermass interest now piqued, he and Roney attempt to uncover its origin. Meanwhile strange occurences and sightings around the dig begin to occur and it becomes clear that the ship is not as inert as it appears. After a compartment is opened and three insectile martians are found, it is deduced that humanity is the result of a failed attempt at colonisation by proxy, by the martians, who have interfered with  early man, producing the larger brained homo sapiens. The martian ship, stimulated by a burst of energy, comes to life, triggering a buried command set deep in the human psyche and the martian colonisation plan begins again, five million years after its inception. The ship emits waves of energy and telepathic command, forcing certain humans still under their control, to purge the weaker and lesser beings to create a 'fixed society' of those who retain the deep mental conditioning. Meanwhile the ship gradually converts itself into an energy form in the shape of a horned demonic martian, as humanity gradually succumbs to its power. Quatermass stuggles against the mental grip, but Roney is unaffected and contrives to steer a chunk of steel into the centre of the energy field - iron being the 'devils old enemy' - and successfully earths the massive alien powersource into the wet ground. As the alien force recedes, a battered humanity picks up the pieces.

4. The Quatermass Conclusion - 1979 ITV series, with John Mills as Quatermass. Probably my least favourite of the series,  a near apocalyptic society, resources are running low, society is coming apart at the seams and anarchy reigns. Quatermass has retired to Scotland, but in a bid to rescue his granddaughter from the chaos, tracks her down to find she has become involved with 'Planet People', a group of hippies who band together and are drawn to ancient stone circles. Following such a group, Quatermass witnesses a gathering at Stonehenge and the strange disappearance of the group under a powerful light from above. Subsequent investigation reveal an alien force is drawing pockets of humanity together to harvest them for food. Cue the usual hurried attempt to prevent the massacre of humanity and Quatermass manages to destroy the alien threat and save the day. Mills looks the part as a weary professor, but the whole performance is generally lacklustre and sensationalised, lacking the BBCs finesse.